1. Field of the Invention
The present invention relates generally to a vacuum process system equipped with a process vessel for carrying out a vacuum process, such as thin-film deposition or etching, for an object to be processed, such as a semiconductor substrate, using a process gas. More specifically, the invention relates to a vacuum process system designed to carry out optical measurement, such as thermometry using a radiation thermometer, of an object to be processed, from the outside via a transparent window provided in a vacuum process vessel.
2. Description of the Related Art
FIG. 4 schematically shows a typical vacuum process system, to which the present invention is applied. This vacuum process system is used for carrying out a vacuum process, such as thin-film deposition or etching, for a substrate S to be processed, such as a semiconductor substrate, using a process gas. In FIG. 4, the vacuum process system is equipped with a process vessel 1 for carrying out the vacuum process for the substrate S housed therein, using a process gas.
To the process vessel 1, a process gas is supplied from a predetermined gas supply means (not shown). The degree of vacuum in the process vessel 1 is held to be a degree of vacuum necessary for the process, by predetermined exhaust means (not shown).
The top of the process vessel 1 is provided with a transparent window 2. Outside of the transparent window 2, there is arranged a radiation thermometer (measuring device) 3 for carrying out the thermometry of the substrate S in the process vessel 1 via the transparent window 2. The radiation thermometer 3 is a kind of optical measuring system for measuring the temperature of an object on the basis of the quantity of thermal radiation from the object.
In the above described conventional vacuum process system, there is the following problem. That is, when the vacuum process, such as thin-film deposition or etching, for the substrate S in the process vessel 1 using the process gas is carried out, the thin-film deposition due to the action of the process gas proceeds on the internal surface of the transparent window 2 facing the interior of the process vessel 1.
By such progress of the thin-film deposition, the light transmittance of the transparent window 2 gradually decreases to deteriorate the precision of the optical thermometry for the substrate S using the radial thermometer 3 via the transparent window 2, so that there is the possibility that it is difficult to carry out the optical thermometry.
In particular, when a pre-coat process or the like for previously supplying a process gas into an empty process vessel 1 before the process to form a uniform thin film in the process vessel 1 is carried out in order to stabilize the state of a predetermined thin-film deposition or the like, the deterioration in the light transmittance of the transparent window 2 due to the thin-film deposition occurs from beginning, so that the above described problem becomes even more serious.